From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Burakov, Anatoly" Subject: Re: [PATCH v2] eal/bus: use RTE_IOVA_PA only if phys addresses are available Date: Mon, 17 Sep 2018 11:33:48 +0100 Message-ID: References: <20180907154703.83316-1-dariusz.stojaczyk@intel.com> <20180907155843.96465-1-dariusz.stojaczyk@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Maxime Coquelin , Chas Williams To: Darek Stojaczyk , dev@dpdk.org, Santosh Shukla , Hemant Agrawal , Jerin Jacob Return-path: Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by dpdk.org (Postfix) with ESMTP id 3CF3011A4 for ; Mon, 17 Sep 2018 12:33:58 +0200 (CEST) In-Reply-To: <20180907155843.96465-1-dariusz.stojaczyk@intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 07-Sep-18 4:58 PM, Darek Stojaczyk wrote: > When neither RTE_IOVA_VA nor RTE_IOVA_PA was explicitly > requested, DPDK would currently fallback to the default > RTE_IOVA_PA mode and possibly encounter a failure later > on if running as a non-priviledged user. Attempting to > use RTE_IOVA_VA if no phys addresses are available may > help in this case. > > Signed-off-by: Darek Stojaczyk > --- > Changes since v1: > * added a missing rte_memory.h include > > lib/librte_eal/common/eal_common_bus.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c > index 0943851cc..68c581b8a 100644 > --- a/lib/librte_eal/common/eal_common_bus.c > +++ b/lib/librte_eal/common/eal_common_bus.c > @@ -37,6 +37,7 @@ > #include > #include > #include > +#include > > #include "eal_private.h" > > @@ -236,9 +237,19 @@ rte_bus_get_iommu_class(void) > mode |= bus->get_iommu_class(); > } > > - if (mode != RTE_IOVA_VA) { > - /* Use default IOVA mode */ > - mode = RTE_IOVA_PA; > + if (mode == RTE_IOVA_VA) > + return RTE_IOVA_VA; > + > + if (mode & RTE_IOVA_PA) { > + /* Not all buses support RTE_IOVA_VA, fallback to RTE_IOVA_PA */ > + return RTE_IOVA_PA; > + } > + > + if (rte_eal_using_phys_addrs()) { > + /* Default to RTE_IOVA_PA only if it's supported */ > + return RTE_IOVA_PA; > } > - return mode; > + > + /* Since RTE_IOVA_PA is unsupported, fallback to RTE_IOVA_VA */ > + return RTE_IOVA_VA; > } > This is a good change, however I think that this is too pessimistic. If i don't have any devices that explictly require IOVA_PA, i should be running in IOVA_VA mode. This of course doesn't take hotplug into account, so a command-line switch to force one or the other should also be available. For example, at startup, i might have devices bound to VFIO, so IOVA_VA mode is picked. However, even though at a time of startup none of the devices require physical addresses, i also know that i might later hotplug a device that requires IOVA_PA (leaving the question of hotplug brokenness aside for now...) - currently, this scenario will not work, as i will be forced to use IOVA_VA mode unless i happen to have a IOVA_PA device available at startup. Similarly, if i'm running DPDK as root but am only using virtual devices like pcap, i should be able to force DPDK into using VA addresses [*], yet currently i will be forced to use IOVA_PA if i don't *also* have a few devices bound exclusively to VFIO. [*] Do we have vdev devices that require IOVA_PA? I can't think of any... -- Thanks, Anatoly